What would the outcome be if i bred a turquoise halfmoon male with a copper doubletail female with a red wash. Tail type and color, what would the fry look like. I would imagine multis with copper in them but i've never seen that before.

Tail type would be half single tail, half double tail. Is your DT a HMDT?

Color wise... since both copper and turquoise are irredecence... I'm going to guess that you will get a mixture of the two colors. I don't think blue and copper meld together so maybe you will get some of each but I don't know. I've never seen the result of that sort of spawn.

I worked only with copper and green/turquoise for a few yrs. Once upon a time gr + cpr = mostly gr. But now the copper gene is stronger so you should have half of each. Since the female has red fins, you should get many red washes in fry..... I prefer solid colors.
(edit) You may also get metallic green ..... a lighter and shiny shade of green.

HM + DTHM = HM and HM with larger dorsals. You should not get any pure DT, only geno's.... but I may be wrong. In the past, you would get DT with uneven lobes .... But lately I don't get those when I cross breed.